A disk drive is a data storage device that stores data in concentric tracks on a recording media disk. During operation, the disk is rotated about an axis by a spindle motor while a transducer (head) reads/writes data from/to a target track of the disk. A servo controller uses servo data read from the disk to accurately position the head above the target track while the data transfer takes place. Cross-track density is an important characterization of the storage capability for a given disk drive. Cross-track density (e.g., tracks/inch) is a function of head design as well as the physical qualities of the recording media. Adjacent and non-adjacent track erasure, which may limit the cross-track density, occurs when data stored on a first track is corrupted by the writing of data to a second track, proximate to the first track. Bit error rate (BER) and data loss specifications for a disk drive may therefore limit the cross-track density and overall storage capacity of a drive.
Automated testing of a magnetic recording media is performed to characterize how much damage occurs in neighboring tracks when a central track is written. Wide area track erasure (WATER) is one automated test which is conventionally based on either error rate or noise amplitude measured across a wide area after tens of thousands of writes to a particular track (i.e. “aggressor track”). A noise-based WATER test assesses the noise the aggressor track writes induce at an off-track position proximate to the aggressor track. However, performing such a large number of writes takes considerable automated tester time, limiting a tester's throughput and limiting the ability to disposition media disks as the disks are produced from a manufacturing line.